人 rén / human, person --> you can see the image of a (headless) human being with one leg stretched out in front
大 dà / big --> the human stretches out both arms, so s/he becomes big
天 tiān / sky, Heaven (the ruling body in the ancient Chinese tradition) --> if the human starts to think s/he is big, above him/her is the sky / Heaven (the ruling body)
太 tài / excessive --> 大 dà is already big, adding one stroke to it makes it too much
